A principal part of any computer system is a data storage device. A disk drive is a typical data storage device. A disk drive generally includes at least one disk of magnetic storage material mounted on a motor shaft or spindle, an actuator that locates a read/write head radially over the disk, and circuitry that is used to read and write data from the disk using the read/write head. A disk drive may also include a controller that interfaces with the computer system while controlling the operation of the disk drive.
The read/write head is typically housed in a “slider.” A slider has a lower surface known as an air bearing surface that opposes the surface of a disk in use. An air bearing surface typically includes rails that extend generally tangential to the disk, and a recessed portion located between the rails. In operation, the rotation of the disk drags air between the rails creating an increase in pressure that pushes upward on the slider forcing the read/write head away from the disk. At the same time, air moving past the recessed portion causes a decrease in pressure that counteracts the pressure effect of the rails. These pressures equalize to so that the slider flies above the disk at a distance referred to as the “fly height.”
The aerial storage density obtainable on a magnetic disk depends directly upon the fly height of the read/write head of a disk drive. Given the ever-present need to increase the storage capacities of disk drives, there is thus a continuous desire to reduce fly heights in order to achieve higher aerial densities.
However, as fly heights are reduced to achieve higher areal densities, external forces such as van der Waals forces, i.e., intermolecular forces that act between electrically neutral molecules, and electrostatic forces exerted on the slider become significant. The presence of metal in the material that the slider is constructed of, e.g., ceramic aluminum titanium carbide (AlTiC), often contributes to the introduction of these forces. At fly heights of a few nanometers, such forces can potentially disrupt the balance of pressures created by an air bearing surface, causing the resulting air bearing to collapse, and allowing the slider to come into contact with the disk.
One approach to reducing the effects of van der Waals and electrostatic forces, and thus allowing a reduction in fly height, is to increase the pitch of the air bearing, so that the lower surface of the slider is not parallel with the disk surface. Another approach is to reduce the size of the trailing edge pads or rails on the air bearing surface. However, both of these approaches require modifying the profile of the air bearing surface, and thus affect the performance of the resulting air bearing. The design of a suitable air bearing surface requires substantial effort, and must accommodate a large number of factors to achieve reliable steady state fly heights of only a few nanometers. Thus, the aforementioned approaches to reducing the effects of external forces introduce additional considerations to the air bearing surface design, and constrain air bearing designers in their ability to manipulate the pressures created by the rails and the recessed portion on the air bearing, thereby impacting the steady state fly height profile.
Therefore, a significant need exists in the art for a slider having an air bearing surface, having a reduced susceptibility to van der Waals and electrostatic forces, and that operates at reduced fly heights without appreciably affecting the steady state fly height profile of the slider or the performance of the air bearing.